Study the G Code interpolation of Linux CNC
- andre
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24 Apr 2017 04:11 #91933
by andre
Study the G Code interpolation of Linux CNC was created by andre
Hello, i don't know if this is a suitable category to post this so please fix me if i'm wrong.
I'm new to CNC and as far as i know, Linux CNC has one of the best interpolations behind those G-Code. I have been searching for documents about linear, circular interpolation.. but they are so fragile and moreover, most of them are about G-Codes definition but not the math behind them.
So there are some keywords i have known until now: DDA, NURBS, XY linear interpolation...
Could you please help where i should start learning about this problem in Linux CNC (documentations, source code...) because i want to make my own simple CNC Machine.
This example to show my purpose:
_ I have 2 points: A(x0,y0), B(x,y).
_ I want my 2 X/Y motors to move with a suitable set of points (interpolation) from A to B quickly, stably.
_ After that i will send pulses to my motors.
So following the idea, my G-Code will look like: G01 A B feedrate... (just an example)
In general, i want to get the set of points for my motors to move following my G-Code
Thank you in advanced !
I'm new to CNC and as far as i know, Linux CNC has one of the best interpolations behind those G-Code. I have been searching for documents about linear, circular interpolation.. but they are so fragile and moreover, most of them are about G-Codes definition but not the math behind them.
So there are some keywords i have known until now: DDA, NURBS, XY linear interpolation...
Could you please help where i should start learning about this problem in Linux CNC (documentations, source code...) because i want to make my own simple CNC Machine.
This example to show my purpose:
_ I have 2 points: A(x0,y0), B(x,y).
_ I want my 2 X/Y motors to move with a suitable set of points (interpolation) from A to B quickly, stably.
_ After that i will send pulses to my motors.
So following the idea, my G-Code will look like: G01 A B feedrate... (just an example)
In general, i want to get the set of points for my motors to move following my G-Code
Thank you in advanced !
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- Todd Zuercher
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24 Apr 2017 13:34 #91959
by Todd Zuercher
Replied by Todd Zuercher on topic Study the G Code interpolation of Linux CNC
I think you may be over thinking this.
If you want your machine to move to point A(x,y coordinates) at feed rate n, your G-code would be
G1 A Fn
Then to move from point A to point B at the same feed rate, you would simply issue
G1 B
To make a program out of it, you could do a G0 positioning move (which will move at the machines maximum rate) to move to point a then use a G1 move to move to point B.
G0 A
G1 B Fn
You don't have to do any math (Linuxcnc is doing all that) all G-code is, is specifying points, and what to do between those points (G1 and G0=move in a straight line)
If you want your machine to move to point A(x,y coordinates) at feed rate n, your G-code would be
G1 A Fn
Then to move from point A to point B at the same feed rate, you would simply issue
G1 B
To make a program out of it, you could do a G0 positioning move (which will move at the machines maximum rate) to move to point a then use a G1 move to move to point B.
G0 A
G1 B Fn
You don't have to do any math (Linuxcnc is doing all that) all G-code is, is specifying points, and what to do between those points (G1 and G0=move in a straight line)
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- andre
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24 Apr 2017 16:19 #91974
by andre
Replied by andre on topic Study the G Code interpolation of Linux CNC
Yeah, i know Linux CNC already has that stuff done. However, i also want to know what the mathematics that our developers use
About the linear interpolation, circular interpolation... I cannot find it in the documentations though..

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- Todd Zuercher
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24 Apr 2017 17:08 #91981
by Todd Zuercher
Replied by Todd Zuercher on topic Study the G Code interpolation of Linux CNC
As far as that goes what I think you're asking for is what the trajectory planner does. That should be reasonably documented somewhere as it was mostly rewritten a couple of years ago. Try asking on the developers mailing list
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24 Apr 2017 22:59 #92010
by andre
Replied by andre on topic Study the G Code interpolation of Linux CNC
thank you Sir! I will try asking them. Have a nice day

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25 Apr 2017 16:35 #92076
by andypugh
Replied by andypugh on topic Study the G Code interpolation of Linux CNC
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